The present invention relates to a steam turbine plant having at least one turbine intake valve and at least one by-pass valve which valves are connected with a live-steam generator by way of a live-steam supply system. A regulating circuit is provided to control the opening or the closing motion of the turbine intake valve and/or the by-pass valve. The regulating circuit is arranged so that it will supply each valve, for the purpose of attaining a specific steam flow-through (the controlled variable), with one electrical signal at a regulating value which acts upon the respective controlled system comprising the valve to be regulated with both of the controlled systems differing from each other in design.
A contractor supplying reactors for nuclear power plants typically specifies that the sum Q.sub.1 (t)+Q.sub.2 (t) for the steam flow-through will remain, at least approximately, constant. This requirement can be met relatively easily in the case of slow changes of the valve openings controlling the flow-through. In the case of rapid reductions in power, however, so-called fast valving, which fast valving is necessary for example in the event of a short circuit or stroke of lightning in one section of the associated network, the turbine intake and by-pass valves must provide very rapid changes in steam flow in opposed directions.
The duration of such fast valving is determined in principle by a known circuit arrangement where x.sub.1 and x.sub.2 represent the electrical signal regulating values for a turbine intake valve and by-pass valve. This is expressed by the formula EQU x.sub.2 (t)=x.sub.3 (t)-x.sub.1 (t) (1.1)
where x.sub.3 is the output signal from a pressure governor, and x.sub.3 (t) is, at least approximately, constant. Therefore: EQU .DELTA.x.sub.2 (t)=-.DELTA.x.sub.1 (t) (1.2)
and .DELTA.Q.sub.2 (t) should, at least approximately, equal -.DELTA.Q.sub.1 (t).
There exist the transfer functions ##EQU1## which are rather complicated and which are not equal due to dissimilar oil systems, servomotors, valves, flow-through conditions, steam pressures, etc. Since F.sub.1 (s).noteq.F.sub.2 (s) and since .DELTA.x.sub.2 (s)=-.DELTA.x.sub.1 (s), then .DELTA.Q.sub.2 (s).noteq.-.DELTA.Q.sub.1 (s) even though .DELTA.Q.sub.2 (t.fwdarw..infin.).apprxeq.-.DELTA.Q.sub.1 (t.fwdarw..infin.), which means that it was not possible heretofore to lower the turbine output upon receipt of a fast valving signal from circuitry within an appropriate time period (approximately one second) to a lesser output value, (for example 35% of the original output) and still meet the requirement of the contractor supplying the nuclear reactor. This requirement being that Q.sub.1 (t)+Q.sub.2 (t) be kept, at least approximately, constant.
Accordingly, it is an object of the present invention to provide a steam turbine plant which is free of the above-discussed disadvantageous features.
A steam turbine plant according to the present invention includes a controlled system having a turbine intake valve and/or a by-pass valve with at least one correction element being arranged according to such a transfer function that the transfer functions of both controlled systems will be, at least approximately, identical with each other.
It is especially advantageous to arrange the correction element within the controlled system which comprises the by-pass valve.
It is still further advantageous if the transfer function (F.sub.KOR (s)) of the correction element follows the formula ##EQU2## and where F.sub.1 (s) represents the transfer function of the controlled system containing the turbine intake valve, x.sub.1 the regulating value acting within this regulating system, F.sub.2 (s) the transfer function of the controlled system comprising the by-pass valve, x.sub.2 the regulating value acting within the last-mentioned system, Q.sub.1 the steam flow through the turbine intake valve, Q.sub.2 the steam flow through the by-pass valve, and s the complex variable.